1. Field of the Invention
The present invention relates, in general, to an adjustable inlet guide vane mechanism for a compressor and, more particularly, to a method of preventing wear of a slot and pin assembly of such an adjustable inlet guide vane mechanism.
2. Description of Related Art
An adjustable inlet guide vane mechanism for a compressor typically includes a plurality of circumferentially arranged vanes, a plurality of operating levers and a control ring. Each operating lever is pivotally mounted at a first end to the control ring by a pin positioned within a slot of the control ring, and each operating lever is mounted at a second end to one of the vanes. Rotation of the control ring causes the levers to adjust the angular position of the vanes.
The slots of the control ring and the pin have typically been machined with straight walls such that a space exists between them when the pin is positioned within the slot. This space exists due to the accuracy of the machining of the slots of the control ring and the pin and for purposes of assembly. This space allows for vibrations between the pin and the slot during operation of the compressor due to air flow on the vanes. Such vibrations create surface damage, in the form of a groove, on the slots of the control ring caused by repeated overload. This surface damage is referred to hereinafter as brinelling type wear.
Over time, a groove in the control ring is caused by the brinelling type wear due to the vibration of the vanes from gas flow. The pin translates vibrations from the vanes to a repeated normal force to the side of the slot of the control ring thereby creating the groove. This groove could cause the pin to lock in the slot leading to a failure of the adjustable inlet guide vane mechanism.
Some attempts have been made to reduce vibrations in compressors. U.S. Pat. No. 7,220,098 to Bruce et al. discloses a compressor variable stator vane assembly (200) resistant to wear due to high temperatures and vibration. The surface of the variable stator vane assembly's (200) vane trunnion (350) is covered with a wear coating (360), which is subsequently covered with an antifriction coating (370). These coatings function to prevent wear of the variable stator vane assembly by providing a reduced coefficient of friction, in the range of 0.2 to 0.6. However, this device, while reducing friction between components, does not reduce vibrations between the pin and slot of the control ring caused by a space created therebetween.
Accordingly, a need exists for an adjustable inlet guide vane mechanism for a compressor that reduces the vibrations caused by a space or gap that exists between the slots of a control ring and the pin positioned therein.